Earlier this month, the first known case of law enforcement requiring a suspect to unlock their phone using Face ID surfaced. Now, Motherboard reports that cops around the United States are receiving instruction to ensure they themselves do not look at an iPhone X or iPhone XS displays, as that could count as one of the ‘false’ trials, and thus disable Face ID.

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Face ID on the iPhone X and iPhone XS will try up to five times to recognize a face, before it locks and requires a passcode to access. The issue law enforcement and investigators are trying to avoid is looking at the display and accidentally wasting one of those five attempts.

Motherboard explains that a presentation from forensics company Elcomsoft, apparently being shown to cops and investigators, highlights this issue and warns cops “don’t look at the screen, or else the same thing will occur as happened [at] Apple’s event.”

This, of course, is a reference to the original iPhone X introduction event in 2017. To kick off the device’s demo, Craig Federighi tried unsuccessfully to unlock an iPhone X using Face ID, but was instead prompted with a passcode. After the event, Apple explained that what had happened was the demo iPhone X had been handled backstage by multiple people, and Face ID had tried to recognize each of those people, but failed since it was looking for Federighi’s face. It ended up failing five times backstage, which is why Federighi was prompted with the passcode interface on stage.

“This is quite simple. Passcode is required after five unsuccessful attempts to match a face,” Vladimir Katalov, CEO of Elcomsoft, told Motherboard in an online chat, pointing to Apple’s own documentation on Face ID. “So by looking into suspect’s phone, [the] investigator immediately lose one of [the] attempts.”

This isn’t the first time law enforcement has been guided to avoid locking an iPhone’s biometric features. With Touch ID, for instance, law enforcement was instructed to always use the power button to turn a device on, not the Home button:

“With Touch ID, you have to press the button (or at least touch it); that’s why we always recommend (on our trainings) to use the power button instead, e.g to see whether the phone is locked. But with Face ID, it is easier to use ‘accidentally’ by simply looking at the phone,” Katalov added.

How to quickly disable Face ID on iPhone X & iPhone XS

Apple makes it very easy to quickly disable Face ID on the iPhone X and iPhone XS in situations where a user would not want someone to be able to hold their device up to their face and unlock it.

To do this, simply press and hold the side button and either power button for several seconds. You’ll then see a slider for powering the device off and Emergency SOS. At this point, Face ID has been disabled and you’ll have to input your passcode to reenable it.